The present application relates to a magnetic material constituted of an Fe alloy used for improving performance of an antenna in, for example, an RFID (radio frequency identification) system, a magnetic sheet constituted of the magnetic material, and a portable electronic apparatus to which the antenna is mounted.
In RFID systems, non-contact-type IC tags in each of which an IC chip on which information is recorded and a resonance capacitor are electrically connected to an antenna coil are known. Regarding the non-contact-type IC tags, there are also card-type IC tags and built-in-type IC tags incorporated into cellular phones and the like.
As an antenna module of the related art used for the non-contact-type IC tags, there is known an antenna module in which a magnetic member (magnetic sheet) is disposed to be substantially in parallel to a plane of a spiral-type flat antenna coil wound on the plane thereof. The antenna module of this type uses a magnetic sheet formed of a material high in magnetic permeability. Due to such a magnetic sheet, an inductance of the flat antenna coil is increased and a communication distance is improved.
An example of a magnetic material used for the magnetic sheet is a magnetic material constituted of an Fe alloy that contains Fe as a primary component, such as an Fe—Si—Al (sendust) alloy and an Fe—Si—Cr alloy. Hereinafter, the magnetic material constituted of an Fe alloy that contains Fe as a primary component may simply be referred to as “Fe alloy magnetic material”. When an additive amount of Si becomes large (e.g., 4.5 wt % (weight percent) or more), the Fe alloy magnetic material is increased in hardness and becomes poor in ductility.
Meanwhile, there are cases where the magnetic sheet as described above is produced by using flattened magnetic particles as a raw material (see, for example, Japanese Patent Application Laid-open No. 2001-284118 (paragraph [0002])) (hereinafter, referred to as Patent Document 1). In flattening processing, magnetic particles each of which has an approximately-spherical shape or a 3-dimensional shape similar thereto are flattened by causing the magnetic particles to collide with steel balls. However, because an increase in additive amount of Si increases the hardness as described above, there is a problem in that a time required for the flattening processing is elongated and the magnetic particles are broken to pieces during the flattening processing. The flattening processing is made additionally difficult when the magnetic particles become small.
Here, a rolling process is enabled by mixing a predetermined amount of P (phosphorous) to the sendust magnetic material (see, for example, Japanese Patent Application Laid-open No. Sho 55-65349 (page 11 of the specification)).